Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$14.69	4.635%	$15.3709	$15.37	$15.35	$15.40
Purchase #2	$202.69	12.782%	$228.5978	$228.60	$228.60	$228.60
Purchase #3	$79.99	12.553%	$90.0311	$90.03	$90.05	$90.00
Purchase #4	$128.61	7.209%	$137.8815	$137.88	$137.90	$137.90
Purchase #5	$70.45	10.819%	$78.072	$78.07	$78.05	$78.10
Purchase #6	$168.29	10.152%	$185.3748	$185.37	$185.35	$185.40
Purchase #7	$221.65	12.194%	$248.678	$248.68	$248.70	$248.70
7 purchase totals =	$886.37		$984.0061	$984.00	$984.00	$984.10